Function stream_process 

pub fn stream_process(
    reader: impl BufRead,
    expression: &Expression,
    as_json: bool,
    as_lines: bool,
    output_format: &OutputFormat,
) -> Result<(), PickError>

Process input as a stream of JSON values (one per line / JSONL). Applies the expression to each value and writes results immediately.

Time: O(n) total where n = input size. Memory: O(1) per line.